Could there be real science behind the old cliche of a woman's biological clock? I didn't believe it -- until now

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It started with a TV commercial. I can’t remember what was being advertised. All I know is that it showed a father holding a newborn baby, and I started to cry — not out of sadness, but awe. A baby, a beautiful baby!

Look, I’m human, and as such, I’ve always found babies cute — but, suddenly, right around my 28th birthday earlier this year, crossing paths with them caused me to grab the arm of my acquaintance as though I’d seen a celebrity. Reactions formerly reserved for baby animals began to apply to human infants. Noticing this shift, a friend who hadn’t seen me for a while remarked, “Since when are you baby crazy?” The real question is: Since when did I become such a cliché?

It’s not that I’m ready to reproduce — good God, no — but I do want to have a baby eventually, though the possibility seems many years off. Will I be ready — emotionally, professionally, financially, romantically — before my fertility nose-dives? This longing feels physically acute — a twitching in my ovaries, an itching in my arms to cradle. In the past, I’d always written off the cliché of the woman in her late 20s or early 30s with a “ticking biological clock” as a sexist trope. Now I find myself reconsidering and wondering how real it is, and why it is.

While common wisdom has it that this desire grows throughout a woman’s 30s, Anna Rotkirch, the director of the Population Research Institute in Finland, says studies have shown “the urge appears to be strongest in the late 20s.” (Dude, I know.) Some women, however, “say they have felt ‘baby fever’ more or less intensely since their early teenage years,” she says. “Other women feel it for the first time in their late 20s.” (You heard it here first: Not all women are the same.)

Rotkirch reported in a paper in the Journal of Evolutionary Psychology that her Finnish interview subjects described the phenomenon in terms of “a painful longing in my whole being” or an “unbelievable aching,” sometimes accompanied by the sensation of having “empty arms” or breasts that “became sensitive and hard.” In a related survey, she found that 58 percent of male respondents and 78 percent of female respondents reported having “experienced a strong desire to have a child of [their] own” — although this seems less a measure of sudden, acute longing than of a general desire to reproduce at some time.

As for why this alleged phenomenon might exist, Rotkirch says we know very little.

“All existing studies use written texts or questionnaires,” she says, which tell us more about how women perceive their “baby lust” rather than the actual origins. Still, Rotkirch has found evidence of a “hormonal underpinning,” she says, with “little influence” of social factors like education or income.

In her paper, she pointed out that, in terms of evolutionary biology, “the ‘default mode’ of the female body is to have experienced both nurturing and pregnancies by the early 20s.” Rotkirch suggested that “longing for a baby can develop as a by-product of hormonal changes that evolved to prepare the woman for motherhood,” she wrote. “Such changes could be induced by falling in love; the ‘nesting behavior’ related to settling down and starting to live with a partner; exposure to infants; and/or by the processes of aging.”

If evolutionary theories are too caveman-y for your taste, there is the undeniable fact that women’s fertility begins to decline in their late 20s, right around the average time that baby panic sets in. She says, “My informed guess is that baby fever is one mechanism for reproductive timing” — or, in other words, a way to urge that “now is a good time to have a baby.” It seems to make intuitive sense, but the science on exactly how this mechanism might work is just not there.

Clearly, though, many women do not ever feel the pull of the ticking clock, or don’t feel it distinctly, and “part of the variation is probably genetic,” she says, “as with most things.” It’s also important to note that men have been found to encounter baby fever too: In an exhaustive study surveying the potential causes of the phenomenon, Gary Brase, an associate professor of psychology at Kansas State University, found that men experience it, just to a lesser degree than women do.

Adding to the lists of “could-bes,” baby fever might just be a “superfluous” feeling arising from “general interest in parenting,” she says. (Although, if a nurturing instinct were the sole explanation, pets would be a far more effective — not to mention cheaper and easier — solution to baby fever.) “At an age were most women in our evolutionary past would have been mothers, or at least surrounded by babies and children, many Western women are not, and this may create a situation where you feel a strong urge to have an outlet and object for your maternal emotions.” Rotkirch points to research on baboons and chimpanzees showing a clear variation in maternal behavior: “Some are very interested in mothering and training to become a mother,” she says, while others are not.

But it’s impossible to ignore the social influence and culture of baby mania — just consider the pregnancy porn in celebrity tabloids and the high-profile exhortations to hurry up and settle down before it’s too late! Then, too, girls are often trained as nurturers from the time they’re in the bassinet. However, Brase, who has studied the issue for nearly a decade, found that beliefs about gender roles — for example, a woman’s conviction that her proper place is in the home — were not strong predictors of baby fever. “Desire for a baby is not strongly connected to people’s gender roles,” he told me.

There is good evidence of a different kind of social influence, though. A Swedish study found that women are more likely to have babies shortly after their co-workers have babies. Is might be a coincidence that my sudden baby ache arrived right around the time that my peers started getting pregnant, or it might not. Within a couple of months of each other, two friends, a family member and a co-worker, all but a handful of years older than me, announced that they had a baby on board. Brase also found that one of the strongest predictors of baby fever was prior positive experiences with babies.

Regardless of whether it stems from our evolutionary roots, there’s no denying that baby fever as a cultural phenomenon or topic of discussion is “a very new and ‘social’ thing,” Rotkirch says. “This is due to the fact that in contemporary developed societies, we grow sexually mature younger but start having babies later than in most other societies through history,” she says. “There is more time to be physiologically mature for a baby without actually having one.”

It’s also the case that women’s greater choices and freedom has resulted in “more ambivalence and decision making,” she says, over whether to have a baby, as well as when and with whom. There are also greater potential barriers related to education and career. Rotkirch found in surveying women that “the longing usually awoke when having a child would theoretically have been possible as the woman was basically healthy and had a satisfying couple relationship,” but “circumstances opposed it, usually the woman’s own life plans, problems in reproductive health, or the attitude of her male partner.”

In an attempt at clarity amid all the hypotheticals, Brase offers, “The short answer is that it is most likely a combination of biology, circumstances and personality.” Does my baby-ache come from a basic, biological imperative? Probably in part. But it’s the tension that results from that urge running up against the constraints of reality that makes it so acute. Without a tension between the two, the ache would simply be an urge put into action.

Overdevelopment, Overpopulation, Overshoot

Overdevelopment, Overpopulation, Overshoot

Slide 13

Airplane Contrails: Globalized transportation networks, especially commercial aviation, are a major contributor of air pollution and greenhouse gas emissions. Photo of contrails in the west London sky over the River Thames, London, England.

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Overdevelopment, Overpopulation, Overshoot

Fire: More frequent and more intense wildfires (such as this one in Colorado, USA) are another consequence of a warming planet.